I'm loading, in my test, 5 textures, but it's dynamic.
It's not the best way to do this with many textures?

Not sure what you mean by dynamic: do you mean the user can select the number of textures at runtime?
After looking at your code a bit more, I think I may have given poor/irrelavant advice in my earlier post, sorry 'bout that: that part of the code I referred does seem to be doing what you
intend it to do.
Here, I'll have another go: here's what I would try(brute force!): The problem might lie in the code you haven't shown: the camera and the ui interaction code.
You could try isolating it by rotating the "camera' automatically in DrawFrame() to see what happens. e.g

Hopefully something like that should continuously rotate the quads.
As long as this code doesn't introduce more bugs, and the first (unwanted) visualisation is eliminated, it may indicate the problem lies in camera/ ui code.
Let us know how you go.

well it appears that the problem persists. And we cannot see all your code. Thus these are the options I would consider next:

(1) fiddle with the code in various places to see what can be done (as we have done), while waiting for help here for a possible prob/solution.
(2) new project: whip up another basic opengl framework or grab one from the many examples that can be found that are known to work, then drop your specific volume rendering code in place of its existing rendering code.

If you have a deadline (as we all do?), and your main goal is to learn about volume rendering rather than opengl programming specifically, all you need is a working opengl rendering frame work to start with. You may never know how long (1) will take if at all. I would go with (2).
(And keep this old project around to debug in you spare time.)

just a shot in the dark:http://stackoverflow.com/questions/1...lder-functions
I noticed that this guy had trouble making glClearColor(... ) work....
After having used freeglut he didn't pay attention to the fact that he now had to link to the opengl library himself.
Have a look at it.